EDM - Electrical Discharge Machining

EDM is a machining method primarily used for hard metals or those that would be impossible to machine with traditional techniques. One critical limitation, however, is that EDM only works with materials that are electrically conductive. EDM or Electrical Discharge Machining, is especially well-suited for cutting intricate contours or delicate cavities that would be difficult to produce with a grinder, an end mill or other cutting tools. Metals that can be machined with EDM include hastalloy, hardened tool-steel, titanium, carbide, inconel and kovar.

Electrical Discharge Machining (EDM) is a machining process used mainly for producing molds . The most common mold found in industry are those used in plastic injection molding. The animation on the right shows the molding process. Plastic granules are melted and fed under pressure into a mold and then cooled. EDM is used extensively in the manufacture of these molds.

EDM can also be used to produce finished parts, such as special shaped cutting tools, parts cut from solid pieces of metal, and other items of complex shapes.

EDM works by using electricity rather than cutting. The electric spark actually vaporizes the metal. The sparks, produced by a spark generator at regular intervals, create a succession of craters in the work piece. In EDM, an electrical discharge is created between the surface of the object and the finishing tool that induces temperatures of between 10,000 and 20,000 degrees centigrade. The size of the crater depends on the energy turned out by the spark generator. The range of the sparks varies from a few microns to 1 mm.

FAMOUS APPLICATION Die sinking EDM Wire cut EDM EDM Miling Wire EDM grinding

APPLICATION

There are two primary EDM methods: ram EDM and wire EDM. The primary difference between the two involves the electrode that is used to perform the machining. In a typical ram EDM application, a graphite electrode is machined with traditional tools. The now specially-shaped electrode is connected to the power source, attached to a ram, and slowly fed into the workpiece. The entire machining operation is usually performed while submerged in a fluid bath. The fluid serves the following three purposes:

flushes material away serves as a coolant to minimize the heat affected zone (thereby preventing

potential damage to the workpiece) acts as a conductor for the current to pass between the electrode and the

workpiece.

In wire EDM a very thin wire serves as the electrode. Special brass wires are typically used; the wire is slowly fed through the material and the electrical discharges actually cut the workpiece. Wire EDM is usually performed in a bath of water.

PROCESS

Die sinking

EDM die sinking reproduces, in a metallic workpiece, the shape of a tool called electrode. Injection molds for plastic parts are very frequently machined by die sinking. The shape given to the electrode is that of the object that is going to be molded. In the machining area, each discharge creates a crater in the workpiece (material removal) and an impact on the tool (wear of the tool/electrode). There is never any mechanical contact between the electrode and workpiece. The electrode is usually made of copper or graphite.

Wire cutting

EDM wire cutting uses a metallic wire (electrode) to cut a programmed contour in a workpiece. Extrusion dies and blanking punches are very often machined by wire cutting. Cutting is always through the entire workpiece. To start machining it is first necessary to drill a hole in the workpiece or start from the edge. In the machining area, each discharge creates a crater in the workpiece (material removal) and an impact on the tool (wear of the tool/electrode). The wire can be inclined, thus making it possible to make parts with taper or with different profiles at the top and bottom. There is never any mechanical contact between the electrode and workpiece. The wire is usually made of brass or stratified copper, and is between 0.02 and 0.03 mm diameter.

Types of applications using EDM

Die sinking

 

 

Wire cutting

 

 

Types of applications using EDM

Industries use EDM.

KELEBIHAN EDM WIRE CUT

Ketepatan yang tinggiEDM menghasilkan ketepatan yang tinggi kerana ia dikawal oleh sistem berkomputer. Ketepatan ukuran adalah sangat jitu berbandingkan dengan proses-proses pemotongan yang lain. Sebarang kesilapan semasa pemotongan tidak berlaku kerana is tidak menggunakan die dan ketepatan yang dihasilkan sangat tinggi.

Hasil produk yang berkualitiKualiti produk yang dihasilkan berkualiti kerana ketepatan dalam pemotongan.Ia juga menggunakan masa yang lama untuk menghasilkan produk, oleh itu penghasilan produk akan bermutu tinggi.

Kurang pembaziranDi sebabkan pemotongan dengan menggunakan sistem berkomputer, ruang-ruang pada produk dapat dikecilkan dan penggunaan semua ruang dapat menjimatkan kos.

Kekerasan dan kekuatanDalam proses ini, produk dipotong dengan menggunakkan dawai panas yang dijana oleh arus elektrik. Produk juga menggunakan penyejuk iaitu air. Oleh itu semasa proses pemotongan ia aka dilindap kejutkan di bahagian permukaan. Maka ia juga sesuai untuk produk yang memerlukkan kekerasan permukaan.

KELEMAHAN EDM WIRE CUT

Masa yang panjang diperlukanProses EDM memerlukan masa yang lama untuk menghasilkan produk yang berkualit. Ia tidak dapat dielakkan dan ini merupakan kelemahan yang utama dalam proses EDM.

Kos yang tinggiKeperluan yang perlu adalah mesin EDM yang semestinya bernilai tinggi seperti penggunaan eletrod, bahan kerja dan sebagainya. Selain itu, tenaga yang digunakan juga banyak seperti tenaga elektrik, sumber air yang digunakan serta kemahiran yang tinggi daripada tenaga pekerja mahir.